For the crumble base:
35g cold unsalted butter
35g demerara sugar
A small pinch of salt
30g plain flour
1½ tsp cocoa powder
For the chocolate cremeux:
155g good quality dark chocolate (70% cocoa solids), in pieces
1 organic/free-range medium egg
90ml whipping cream
150ml whole milk
For the caramel hazelnuts:
400g whole hazelnuts (skin on)
180g caster sugar
A pinch of sea salt
For the lime butterscotch sauce:
180ml whipping cream
180g caster sugar
75g freshly squeezed lime juice, heated
5g finely grated lime zest
10g fresh ginger, peeled and finely grated
Sea salt and freshly ground black pepper
- For the crumble base, preheat the oven to 170C/Gas 3. Stand an 18cm tart ring on a baking tray lined with greaseproof paper. Pulse all the ingredients together in a food processor for a few seconds, to a crumble texture.
- Sprinkle the crumble evenly into the tart ring and press down lightly. Bake for 10-12 minutes. Remove from the oven and set aside to cool.
- For the cremeux, melt the chocolate in a bain-marie. Lightly beat the eggs in a medium bowl. Bring the cream and milk to the boil, then pour onto the egg, whisking all the time. Slowly whisk this mixture into the melted chocolate. Leave to settle; skim off any bubbles. Pour the chocolate mixture over the crumble base in the tart ring. Let cool for 30 minutes, then refrigerate for 6-24 hours.
- For the caramel hazelnuts, heat the oven to 180C/Gas 4. Scatter the nuts on a baking tray and roast for 10 minutes. Leave to cool, then wrap the nuts tightly in a cloth and rub to remove the skins. Pick out the nuts and set aside.
- Put the water in a medium pan, add 100g of the sugar and leave for a few minutes. Heat, stirring, to melt the sugar and cook to a dark caramel. Carefully add the hazelnuts and salt, turn the nuts with a spoon to coat in the caramel, then tip onto a greased tray and leave to cool for 1 hour.
- When the caramel hazelnuts are set firm, break them up. Put 250g into a food processor and pulse to a coarse texture; do not grind to a powder. Set aside. Reserve the remaining whole caramel hazelnuts for decoration.
- For the sauce, bring the cream to the boil in a small pan. Put the water into another, large saucepan, add the sugar and leave for a few minutes. Now heat, stirring, to melt the sugar evenly, then let it colour to an amber caramel. Carefully pour in the hot lime juice, lime zest and grated ginger, followed by the hot cream; it will bubble fiercely. Stir well and bring back to the boil. Cook for 3-4 minutes until thick enough to coat the back of a spoon. Add a pinch each of salt and pepper. Let cool, then refrigerate.
- To serve, once the chocolate cremeux has set, warm the ring with a cook’s blowtorch and lift it from the tart. With a warm knife, cut the tart into slices. Top with a quenelle of creme fraiche and serve with the lime butterscotch sauce and a scattering of caramelised hazelnuts.